In-situ conformable triaxial braided structure

ABSTRACT

Triaxial braided structures are prepared according to one or more conformance orientations that facilitate conformability to a variety of shapes during deployment.

CROSS-REFERENCE TO RELATED APPLICATION

This patent application claims priority to and the benefit of pendingprovisional patent application 62/057,618 filed on Sep. 30, 2014 whichis incorporated by reference herein in its entirety.

TECHNICAL FIELD

The present subject matter relates generally to braided structures. Moreparticularly, the present subject matter relates to triaxial braidedstructures conformable to various surfaces.

BACKGROUND

Braided structures are used extensively in the manufacture of compositeparts as reinforcements materials embedded in a resin matrix. It is alsoknown to use braided structures as distinct components within anassembly of parts, for instance, as a blade-out containment component ina jet engine component. Braided structures are often preferred overother types of structures, such as woven structures, because tows ofmaterial within the structure can be oriented along non-perpendiculardirections and the structures can either conform to a surface uponapplication or be manufactured in to conform to a specific surface.

SUMMARY

Aspects disclosed include a braided structure comprising a series oflongitudinal tows extending in a braided structure longitudinaldirection, a first series of bias tows extending in a first biasdirection, and a second series of bias tows extending in a second biasdirection. The series of longitudinal tows, the first series of biastows, and the second series of bias tows are woven to define the braidedstructure, and the braided structure is arranged according to aconformance orientation. The conformance orientation is not whollyaligned with the braided structure longitudinal direction, the firstbias direction, or the second bias direction, and the conformanceorientation is configured to conform to an irregular structure.

In further embodiments of the innovations, a method for forming abraided structure is disclosed. The method includes providing a seriesof longitudinal tows, providing a first series of bias tows, andproviding a second series of bias tows. The method also includesbraiding the series of longitudinal tows, the first series of bias tows,and the second series of bias tows into a braided structure such thatthe longitudinal tows as braided extend through a braided structurelongitudinal direction. The first series of bias tows extend through afirst bias direction, and the second series of bias tows extend througha second bias direction. Thereafter, the method includes cutting thebraided structure according to a conformance orientation. Theconformance orientation is not wholly aligned with the braided structurelongitudinal direction, the first bias direction, or the second biasdirection, and the conformance orientation is configured to conform toan irregular structure.

There is also disclosed a method of forming a braided structure. Themethod includes providing a series of longitudinal tows, providing afirst series of bias tows, and providing a second series of bias tows.The method also includes braiding the series of longitudinal tows, thefirst series of bias tows, and the second series of bias tows into abraided structure. The longitudinal tows as braided extend through abraided structure longitudinal direction, the first series of bias towsextend through a first bias direction, and the second series of biastows extend through a second bias direction. The braided structure isbraided according to a conformance orientation, and the conformanceorientation is not wholly aligned with the braided structurelongitudinal direction, the first bias direction, or the second biasdirection. The conformance orientation is configured to conform to anirregular structure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an example triaxial braided structure;

FIG. 2 illustrates a conformance orientation in relation to a triaxialbraided structure;

FIG. 3 illustrates a triaxial braided structure arranged in aconformance orientation; and

FIG. 4 illustrates a triaxial braided structure prepared according to aconformance orientation as applied to a curved object.

DETAILED DESCRIPTION

Braided structures are comprised of two or more sets of tows wherein thetows within each set are generally parallel at the time of manufactureif formed on a cylindrical surface whose axis is parallel to thelongitudinal direction of the braided structure. The tows in each set oftows are generally each intertwined with tows in the opposing set in arepetitive pattern.

The terms “strand”, “tow”, “yarn”, “yarn bundle”, “fiber” and “fiberbundle” are generally meant to describe what is laid into or intertwinedin each of the principal directions of a braided structure. In thisdisclosure the term “tow” will generally be used to describe what islaid into or intertwined in each of the principal directions of abraided structure. A tow is an amalgamation of all material that runstogether in a principal direction. A tow can comprise monofilaments,multiple filaments or be comprised of staple, or spun, material. Towmaterial can have a variety of cross-sectional shapes, including but notlimited to, generally circular, ellipsoidal, triangular and flat tapeshapes. Tow material may be subject to intermediate or pre-processingprior to braiding operations. Examples of intermediate or pre-processingmay include, but are not limited to, twisting, braiding small numbers offilaments into braided tow materials, pre-impregnation with resins andspecialty coating to facilitate braiding and/or subsequent processing. Atow can comprise any combination of these materials and material forms.Any one tow may comprise one or more filament or staple materials. Asnon-limiting examples, a tow may be comprised of carbon materials,basalt, glass materials, thermoplastic polymeric materials, thermosetpolymeric materials, a combination of carbon and polymeric materials ora combination of polymeric and glass materials, or some combinationthereof.

Common terms used to describe braided structures are based on aCartesian system of directions and rotations as applied to a planesurface considered to be formed from cylindrical surface after it isslit in the direction of the cylinder axis and the cylindrical surfacerolled out into a plane.

The longitudinal direction of braided structures is often used as areference direction when describing the orientations of sets of tows inthe braided structure. The longitudinal direction is often referred toas the axial direction. Directions oblique to the longitudinal directionare often referred to as bias directions. Oblique directions oriented atangles clockwise to the axial direction are generally referred to aspositive bias directions and those oriented at angles counterclockwiseto the axial direction are generally referred to as negative biasdirections.

Biaxial braided structures have two sets of tows, one oriented along apositive bias direction and the other along a negative bias direction. Atypical shorthand description of the orientations of the two sets withina biaxial braided structure is comprised of a positive and a negativenumber each numerating the bias angle for a set of tows. For example, abiaxial braided structure called Bimax, manufactured by A&P technology,Inc., is designated as a +45°/−45° braid.

An inherent feature of biaxial braided structures is that the towscomprising the braided structure can move relative to one another andallow the braided structure to conform to a range of surfaces withoutcompromising the braided structure or the tows. After conformation to aspecific surface the general relative orientation of tows within setsand set to set is maintained and may be best understood by consideringthe Cartesian system to have been mapped onto the surface.

Triaxial braided structures have three sets of tows. Two sets areoriented as described for biaxial structures. The third set of tows isoriented along the axial direction and intertwined with the first andsecond set of tows. A typical shorthand description for a triaxial braidstructure includes the angular orientation of each tow set relative tothe axial direction and the axial direction itself to better convey thatthe braided structure is triaxial. For example, a triaxial braidedstructure marketed as Qiso, manufactured by A&P Technology, isdesignated as a +60°/0°/−60° braid structure.

The addition of axial tows restricts relative motion of tows therebygenerally locking the structure in the as-manufactured geometry.Triaxial braided structures are generally used in sheet or tubular formor are manufactured to conform to a specific surface at the time ofmanufacture.

Triaxial braided structures may be manufactured to conform to a specificsurface at the time of manufacture by overbraiding onto a specificsurface so that the locking action of the axial tows occurs as thebraided structure is laid on the surface and the geometry of the braidedstructure assumes and retains its as-manufactured configuration.

Once manufactured, it is difficult to apply a triaxial braided structureover a surface different from that as-manufactured surface withoutincurring folds, undulations, bunching and similar defects.

There is a need for a triaxial braided structure that can conform insitu to a range of surfaces after the point of manufacture withoutincurring folds, undulations, bunching and similar defects. An in-situconformable triaxial braided structure may conform to a range ofsurfaces with the axial and bias tows generally following pathsapproximating the structure in the Cartesian plane mapping onto theconform surface.

The triaxial braided structure of the present subject matter provides arange of in-situ conformability after manufacture. The braided structureis comprised of at least one layer of triaxial braided material, saidlayer comprised of tows laid in along two oblique, or bias, angles andtows laid along the longitudinal direction and intertwined with the biastows. The triaxial braided structure may be manufactured in a sleeveform by conventional means and single or doubly slit and laid flat toform a conventional triaxial broadgood.

The triaxial broadgood may then be trimmed at an oblique angle not equalto the bias angle to form a triaxial broadgood with non-equal biasangles. For example, a +60°/0°/−60° triaxial broadgood may be trimmed atan angle, relative to the axial direction, between 0° and 30° degreesinclusive. After trimming the longitudinal direction of the fabric liesparallel to the trimline and the resulting braid structure ischaracterized by the directions of the two oblique bias tows and oneaxial tow relative to the new longitudinal direction of the fabric. Forexample, trimming the +60°/0°/−60° triaxial broadgood at 30° relative tothe original longitudinal direction of the fabric in a preferredembodiment of the present subject matter results in a braid architecturecharacterized as +90°/30°/−30°. This embodiment results in the shortestfiber lengths in each of the principal directions of the fabric.

To assist with understanding of the triaxial braided structure, FIG. 1illustrates an example embodiment. Braided structure 100 includeslongitudinal tow 101, positive bias tow 102, and negative bias tow 103.Longitudinal tow 101 extends in braided structure longitudinal direction104 and is one in a series of similarly arranged tows. Positive bias tow102 is one in a series of positive bias tows with an angular orientationclockwise 106 to braided structure longitudinal direction 104. Negativebias tow 103 is one in a series of negative bias tows with an angularorientation counterclockwise 107 to braided structure longitudinaldirection 104. Depending on the braiding technique, these braidedstructures can be at least partially self-locking as described aboveinasmuch as the individual tows may resist unraveling due tointerlocking friction between the braided tows.

Braided structure 100 or other braided structures can be modified toplace the braided structure in a conformance orientation. A conformanceorientation, as used herein, is an arrangement of a braided structurecalculated to best conform to irregular shapes. In this regard, having alongitudinal tow or bias tow incident to a particular surface of anirregularly-shaped object to which the braided structure is deployed maypermit the braided structure to most flatly overlay the object, avoidingbunching or pulling. Depending on, e.g., a radius of curvatureassociated with the irregularly-shaped object, particular conformanceorientations may be more suited for deploying braided structures thanothers. In embodiments, particular conformance orientations can bedetermined to cover ranges of curvature for irregularly-shaped objects.In embodiments, a conformance orientation can include cutting asubsection from a braided structure at angle(s) to the tows of thestructure. In further embodiments, parallel cuts can be madeestablishing a new lengthwise braided structure in accordance with theconformance orientation such that the edges of the structureestablishing its length or width are not aligned with at least thelongitudinal tows. In an alternative embodiment, the braided structurecan be braided according to the conformance orientation such that thelongitudinal tows extend at angle(s) to outer edges of the braidedstructure, thus obviating the need to cut the braided structure toachieve the conformance orientation.

Depicting a cutting embodiment, FIG. 2 illustrates a plan view of aschematic representation of a +60°/0°/−60° triaxial braided structure200 trimmed along at least a first trimline 211 at a conformance anglerelative to the original longitudinal direction defined by longitudinaltows 201 of the fabric. By cutting braided structure 200 at theconformance angle, a conformance orientation can be accomplished. In theillustrated embodiment, the conformance angle is approximately 30° andthe resultant braid architecture is characterized relative toconformance longitudinal direction 204 as a +90°/30°/−30° braid. Theconformance orientation can further be accomplished by cutting alongsecond trimline 212, third trimline 213, and fourth trimline 214 toprovide a rectangular cutout from the original braided structure 200. Inthis regard, the longitudinal direction of longitudinal tows 201 inreference to the overall shape of braided structure 200 in FIG. 2establishes an arbitrary orientation agnostic to the end product towhich braided structure 200 will be applied, and braided structure 200can (but need not exclusively) be prepared in a conformance orientationby cutting.

Turning to FIG. 3, the triaxial braided structure according to theconformance orientation 200′ has a range of conformability making itparticularly suitable for composite layup of arcuate shapes. The newlongitudinal direction of the structure 204′, which defined theconformance angle, is on angle to longitudinal tows 201′, positive biastows 202′, and negative bias tows 203′. Such arcuate shapes can includethose such as deployed to, e.g., composite fuselage frames for aircraft.The range of conformability is determined at least in part by theability of the free ends of the tows in each of the principal directionsto withdraw from the edge to allow for some change in relative lengthsof tows as the trimmed triaxial braided structure follows the curvatureof the form over which it is laid.

While FIG. 3 illustrates the conformance orientation as being based onsubstantially straight cuts through a braided structure to define newstructure edges and tow angles with respect to such edges, various otherconformance orientations can be utilized. Whether through cutting or bymanufacturing a braided structure such that the tows are arranged at anangle to one or more edges in the un-cut form, the edges of the braidedstructure in the conformance orientation need not be straight,symmetrical, or regular, and can include straight, curved, sawtooth orzig-zag, or other arrangements in at least one direction to best permitthe desired flexibility in the conformance orientation.

In this regard, while the above description of FIG. 3 describes anembodiment where a previously braided structure is cut to a conformanceorientation, braided structure 200′ can be braided in the orientationshown in some embodiments to obviate the need for cutting the braidedstructure to achieve geometries supporting the conformance orientation.In this regard, the braided structure longitudinal tows (or others)would be produced in a manner such that their direction through thebraided structure does not align with edges or sides of the braidedstructure.

Either to reduce or prevent unraveling of unfinished ends after braidingor cutting, an edge treatment can be applied. The edge treatment caninclude the temporary application of removable adhesives such as a tapeor other solid-backed removable adhesive. The adhesive can be selectedbased on its strength of adhesion such that it will prevent undesiredunraveling but permit edges to displace appropriately when deploying thebraided structure in the conformance orientation to an irregular object.

Other possible edge treatments include hot melting loose edges, applyingnon-removable adhesives, and/or the inclusion of one or more edge towsbraided near an outer edge (as-braided or after cutting) of a braidedstructure in a conformance orientation to prevent unraveling. Thestrength of the edge treatment can be prepared to permit more (e.g., hotmelt securing edges entirely) or less (e.g., hot melt that allows towsto be pulled loose from edges and resultant movement within structure)flexibility in the edges while avoiding undesired loss of braiding.

FIG. 4 shows a braided structure 410 laid around a curved object 420. Inthis regard, braided structure 410 has been cut to a conformanceorientation such that braided structure 410 can be laid over curvedobject 420 without bunching or other undesired effects. After being laidaround curved object 420, braided structure 410 can be secured in itscurrent form, or undergo additional processing/post-processing steps(such as, e.g., resin application) to complete its deployment to curvedobject 420.

In further embodiments of the innovations, a method for forming abraided structure is disclosed. The method includes providing a seriesof longitudinal tows, providing a first series of bias tows, andproviding a second series of bias tows. The method also includesbraiding the series of longitudinal tows, the first series of bias tows,and the second series of bias tows into a braided structure such thatthe longitudinal tows as braided extending through a braided structurelongitudinal direction, the first series of bias tows extending througha first bias direction, and the second series of bias tows extendingthrough a second bias direction. Thereafter, the method includes cuttingthe braided structure according to a conformance orientation. Theconformance orientation is not wholly aligned with the braided structurelongitudinal direction, the first bias direction, or the second biasdirection, and the conformance orientation is configured to conform toan irregular structure.

An alternative method can include providing a series of longitudinaltows, providing a first series of bias tows, and providing a secondseries of bias tows. The method also includes braiding the series oflongitudinal tows, the first series of bias tows, and the second seriesof bias tows into a braided structure. The longitudinal tows as braidedextend through a braided structure longitudinal direction, the firstseries of bias tows extend through a first bias direction, and thesecond series of bias tows extend through a second bias direction. Thebraided structure is braided according to a conformance orientation, andthe conformance orientation is not wholly aligned with the braidedstructure longitudinal direction, the first bias direction, or thesecond bias direction. The conformance orientation is configured toconform to an irregular structure.

While the above generally describes triaxial braided structures, it isappreciated that biaxial structures, or structures having four or moretow directions, can be utilized in particular embodiments as well

While the above subject matter has been illustrated and described indetail in the drawings and foregoing discussion, the same is to beconsidered as illustrative and not restrictive in character, it beingunderstood that exemplary embodiments have been shown and described andthat all changes and modifications that come within the spirit of theinvention are desired to be protected by the appended claims andequivalents thereof.

What is claimed is:
 1. A braided structure, comprising: a series oflongitudinal tows extending in a braided structure longitudinaldirection; a first series of bias tows extending in a first biasdirection; and a second series of bias tows extending in a second biasdirection, the series of longitudinal tows, the first series of biastows, and the second series of bias tows woven to define the braidedstructure, the braided structure arranged according to a conformanceorientation, the conformance orientation is not wholly aligned with thebraided structure longitudinal direction, the first bias direction, orthe second bias direction, the conformance orientation is configured toconform to an irregular structure.
 2. The braided structure of claim 1,the braided structure is braided as a continuous structure of arbitraryorientation and cut to the conformance orientation.
 3. The braidedstructure of claim 1, further comprising an edge treatment applied aftercutting.
 4. The braided structure of claim 3, the edge treatmentincludes a removable adhesive.
 5. The braided structure of claim 1, thebraided structure is braided to the conformance orientation.
 6. Thebraided structure of claim 1, the conformance orientation includes aconformance angle defined by at least one edge of the braided structurein the conformance orientation.
 7. The braided structure of claim 6, thebraided structure is rectangular and the conformance angle is an angledefined by at least two parallel cut edges in relation to the braidedstructure longitudinal direction.
 8. The braided structure of claim 1,the conformance orientation varies along at least one dimension of thebraided structure.
 9. The braided structure of claim 8, the conformanceorientation includes a curve along at least one edge of the braidedstructure.
 10. A method of forming a braided structure, comprising:providing a series of longitudinal tows; providing a first series ofbias tows; providing a second series of bias tows; braiding the seriesof longitudinal tows, the first series of bias tows, and the secondseries of bias tows into a braided structure, the longitudinal tows asbraided extending through a braided structure longitudinal direction,the first series of bias tows extending through a first bias direction,and the second series of bias tows extending through a second biasdirection; and cutting the braided structure according to a conformanceorientation, the conformance orientation is not wholly aligned with thebraided structure longitudinal direction, the first bias direction, orthe second bias direction, the conformance orientation is configured toconform to an irregular structure.
 11. The method of claim 10, furthercomprising treating at least one edge of the braided structure aftercutting the braided structure according to the conformance orientation.12. The method of claim 11, wherein treating the at least one edge ofthe braided structure includes applying a removable adhesive.
 13. Themethod of claim 10, the conformance orientation is an angle defined byat least one direction of a cut with reference to the braided structurelongitudinal direction.
 14. The method of claim 13, the braidedstructure is rectangular and the conformance angle is the angle definedby at least two parallel cut rectangular edges in relation to braidedstructure longitudinal direction.
 15. The method of claim 10, theconformance orientation varies along at least one dimension of thebraided structure.
 16. A method of forming a braided structure,comprising: providing a series of longitudinal tows; providing a firstseries of bias tows; and providing a second series of bias tows; andbraiding the series of longitudinal tows, the first series of bias tows,and the second series of bias tows into a braided structure, thelongitudinal tows as braided extending through a braided structurelongitudinal direction, the first series of bias tows extending througha first bias direction, and the second series of bias tows extendingthrough a second bias direction, the braided structure braided accordingto a conformance orientation, the conformance orientation is not whollyaligned with the braided structure longitudinal direction, the firstbias direction, or the second bias direction, the conformanceorientation is configured to conform to an irregular structure.
 17. Themethod of claim 16, further comprising treating at least one edge of thebraided structure after braiding the braided structure according to theconformance orientation.
 18. The method of claim 17, wherein treatingthe at least one edge of the braided structure includes applying aremovable adhesive.
 19. The method of claim 16, the conformanceorientation is an angle defined by at least one direction of a cut withreference to the braided structure longitudinal direction.
 20. Themethod of claim 16, the conformance orientation varies along at leastone dimension of the braided structure.